Process of reducing metals from their solutions.



No. 788,584. PATENTED MAY 2, 1905.

G. B. JACOBS. PROCESS OF REDUCING METALS FROM THEIR SOLUTIONS.

APPLICATION FILED JUNE 8. 1900. RENEWED SEPT. 16, 1904- aiues'aea, Zea/63w iTEn STATES Patented May 2, 1905.

PATENT OEEICE.

' CHARLES E. JACOBS, OF EAST ORANGE, NEW JERSEY. ASSIGNOR TO THE AMPEREELEOTRO-OHEMIOAL COMPANY, OF PORT CHESTER, NEW YORK, A CORPORATION OFNEW YORK.

PROCESS OF REDUCING METALS FROM THEIR SOLUTIONS.

SPECIFICATION forming part of Letters Patent No. 788,584, dated May 2,1905. Application filed June 8, 1900. Renewed September 16,1904:- SerialNo. 224,682.

'10 (bl/Z whom it may concern: I

Be it known that I, CHARLES E. JACOBS, a citizen of the United States,and a resident of East Orange, county of Essex, State of New Jersey,have invented certain new'and useful Improvements in Processes ofReducing Metals from Their Solutions, of which the following is aspecification.

This invention. relates to the reduction of gold from its solutions, andmore especially to the reduction of gold from its cyanid. and chloridsolutions by means of a novel treatment with phosphide of hydrogen.

The invention depends for its controlling I 5 principle upon thepowerful action of gaseous phosphide of hydrogen on acid solutions ofchlorid of gold and on solutions of aurocyanic acid.

This invention is an improvement on the process of reducing metals fromtheir solu tions granted me in United States Letters Patent N 0.624,040, in which process I operated with phosphide of hydrogen onsolutions of gold and silver (together with the various base metals thatmay occur associated. in the ores of gold and silver) in which an alkalior an alkaline material was present, precipitating the gold and silverin a metallic state and the base metals as phosphides, in which. formthe gold and silver may be readily separated from the base-metalphosphides by means of suitable fluxes in the ordinary Way of obtainingbullion. I have now discovered that if the solutions containing thenoble 3 5 metals together with base metals be made acid before thetreatment with phosphide of hydrogen the base metals are entirelyunaffected and that only the noble metal. is acted upon by phosphide ofhydrogen. I pre- 4 for to use muriatic acid to make the solutions acid.In case the silver is present with the gold the silver is at onceprecipitated as silver chlorid and is filtered off and reducedseparately from the gold by the ordinary means of reducing silverchlorid. The acid solution containing the gold and base metals is thensubjected to the action of phosphide of hydrogen, which brings the golddown as a precipitate and leaves the base metals unaffected andremaining in solution. With chlorid-of-gold solutions the reaction is asfollows:

lAuOl, H01 ZPII, ZPOL, 7HO1+ lAu.

Metallic gold is precipitated, and the base metals when present remainin solution, as the presence of the free hydrochloric acid preventstheir precipitation as phosphides, in which form they are precipitatedin neutral or alkaline solutions.

In dealing with. cyanid solutions of gold, for which the process isespecially designed, two sets of reactions take place, the first ofwhich is as follows:

KALKODZ) +1101 =HAu(Cn Him,

the result of which is the formation of aurocyanic acid, HAu(On Whenaurocyanic acid is subjected to the action of gaseous phosphide ofhydrogen, the following reaction takes place:

A phosphide of gold is precipitated, which methods of eXact analysishave shown to have the formula AuP lH O. All base metals which werepresent remain in solution.

The hydrocyanic acid formed by the above reaction and also that which isproduced by the action of the hydrochloric acid on the excess ofpotassium cyanid, which is always present in cyanid mill solutions, isconverted by treatment with caustic-potash solutions into potassiumcyanid for use in the treat ment of fresh ores. The precipitate consisting of metallic gold in the case of chlorid solutions and of phosphideof gold in the case of cyanid solutions is heated at a low heat to driveoff phosphorus and anneal the gold, so that it may be handled withoutmechanical loss. The gaseous precipitant is produced by putting calciumphosphide into water and collecting the phosphide of hydrogen therebyproduced in a gas-holder, from which it is led and distributedthroughout the solution by any suitable apparatus.

My invention therefore comprises a method of precipitating the noblemetals from solutions containing them in the presence of base metals bytreating such solutions, and particularly cyanid solutions, withphosphide of hydrogen after the solutions have been made acid,preferably with hydrochloric acid.

The accompanying drawing illustrates an apparatus for carrying out mymethod. It comprises a telescope gas-holder formed of galvanized iron orsteel in two sections 1 and 2, arranged to telescope together, bracketsbeing mounted upon the inside of the stationary portion 2 to form asupport for the movable portion 1 when it reaches its lowest position.From the stationary member of the tank at a point near the bottomextends a spout 3, and from the top of the movable member leads a pipe4, controlled'by a stop-cock, from which gas may be led through aflexible pipe to a distributing-tube 5, from which the gas may bedistributed through the solution contained in a tank 6. The tank islined with a flexible material, such as canvas, (indicated at 7.)Phosphide of calcium may be introduced into the gas-holder through thespout 3 and will be slowly decomposed by the water into calcium hydrateand hydrogen phosphide, which collects in the space above the tank andgradually displaces the water with which the tank is filled at thecommencement of the operation. In tank 6 is placed the mill solutioncontaining silver or gold, or both together, with the base metals afterit has been made acid with hydrochloric acid in a tank of exactlysimilar construction. In case of silver being present it is precipitated and removed from the solution as silver chlorid. Basemetals-such as copper, antimony, zinc, iron, &c .-which may be presentin the same solution are not aflected in the presence of freehydrochloric acid by phosphide of hydrogen, while the gold is quicklyand completely precipitated. I prefer to line the tank with cloth orcanvas of fine mesh to trap the precipitate and allow the solution todrain off. During the operation sample tests should be made from time totime, and when all of the gold has been thrown down the gas should beturned off and the canvas removed from the tank. The precipitate is thenwashed and removed to a clay crucible and dried, first by a slow heatand then the temperature raised to an annealing heat to cement theparticles of gold together.

As an example of the practical operation of the process a cyanid millsolution corresponding to one ounce of gold per ton of solution was usedin which ten ounces of cop-' per and iron had been dissolved. .989.ounce of fine gold was recovered, in which no trace of iron or coppercould be found. The consumption of raw materlals was as follows:

6.24 pounds of calcium phosphide per ton of solution and .75 pound ofhydrochloric acid per ton of solution. 1.5 pounds of caustic potash wasused in the regeneration of potassium cyanid. Fifty per cent. of theoriginal potassium cyanid was recovered. An extremely dilute solutionwas then made on the basis of one ounce of gold to twenty-five tons ofsolution. In practice mill solutions do not often run below one ounce ofgold to six or seven tons of solution. 96.5 per cent. of the gold wasrecovered in a pure state. The consumption of the phosphide wasproportionately the same as in the first example cited.

The advantage of my process as applied to cyanid solutions in particularover the zinc method of precipitation and over the phosphide method inalkaline or neutral solutions are: the entire absence of base metals inthe precipitates obtained and the extreme purity of the resultingbullion the elimination of loss in values due to necessary smeltingprocesses when base metals exist with the precious metals; the avoidanceof the difliculty of handling the great bulk of raw material in theZinc-boxes without loss; the application of the cyanid treatment toores, which under the zinc method are not applicable to that methodowing to the presence of certain base metals. The unavoidabledisadvantages of the zinc method, such as the selective action in theZinc-boxes and use of weak-solution boxes, are entirely eliminated bythe phosphide method. Broadly, the phosphide method of precipitationovercomes the many disadvantages of the Zinc process and at the sametime renders the precipitation cheaper, operates more rapidly, producesa fine bullion, and broadens the application of the cyanid treatment.

Having thus described my invention and set forth its advantages, what Iclaim as new, and desire to secure by Letters Patent, is-

1. The process of separating gold, from base metals,in cyanid solutionscontaining gold and base metal, consisting in subjecting the solution tothe action of gaseous phosphide of hydrogen, in the presence of freeacid, thereby precipitating the gold while retaining the base metal insolution.

2. The process of separating gold from base metals in cyanid solutions,consisting in acidifying the solution containing gold and base metalwith hydrochloric acid and subjecting said solution to the action ofgaseous phosphide of hydrogen.

3. The process of precipitating gold from its cyanid solutions,consisting in acidifying the solution containing gold and base metalwith hydrochloric acid, thereby forming aurocyanic acid and thensubjecting the solution to the action of gaseous phosphide of hydrogen.

4. The process of separating gold from base metals in cyanid soliitionsconsisting in acidifying with hydrochloric acid and subjecting thesolution to the action of gaseous phos hide of hydrogen, therebyprecipitating [o the p osphide of gold, While the base metals remain insolution, and heatin the phosphide of gold to eliminate the phosp liorus.

CHARLES B. JACOBS.

Witnesses:

HARRY E. KNIGHT, J. GREEN.

